Analytic evaluation of diffuse fluence error in multi-layer scattering media with discontinuous refractive index

A simple analytic method of estimating the error involved in using an approximate boundary condition for diffuse radiation in two adjoining scattering media with differing refractive index is presented. The method is based on asymptotic planar fluences and enables the relative error to be readily evaluated without recourse to Monte Carlo simulation. Three examples of its application are considered: (1) evaluating the error in calculating the diffuse fluences at a boundary between two media with differing refractive index and dissimilar scattering properties (2) the dependence of the relative error in a multilayer medium with discontinuous refractive index on the ratio of the reduced scattering coefficient to the absorption coefficient ms'/ma (3) the parametric dependence of the error in the radiant flux Js at the surface of a three-layer medium. The error is significant for strongly forward biased scattering media with non-negligible absorption and is cumulative in multi-layered media with refractive index increments between layers.Comment: 21 pages 7 Figures Text further revise

Calibration of a fission gas monitor

Calibration of argon gas neutron activation sampling devic

Heart Memories

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On Two Models of the Light Pulse Delay in a Saturable Absorber

A comparative analysis of two approaches to description of the light modulation pulse delay in a saturable absorber is presented. According to the simplest model, the delay of the optical pulse is a result of distortion of its shape due to absorption self-modulation in the nonlinear medium. The second model of the effect, proposed at the beginning of our century, connects the pulse delay with the so-called "slow light" resulting from the group velocity reduction under conditions of the coherent population oscillations. It is shown that all the known experimental data on the light pulse delay in saturable absorbers can be comprehensively described in the framework of the simplest model of saturable absorber and do not require invoking the effect of coherent population oscillations with spectral hole-burning and anomalous modifications of the light group velocity. It is concluded that the effect of group velocity reduction under conditions of coherent population oscillations has not received so far any experimental confirmation, and the assertions about real observation of the "slow light" based on this mechanism are groundless.Comment: Regretfully, the journal version of the paper (in Optics and Spectroscopy) appeared to be strongly corrupted due to ignorant editing. In particular, "coherent population oscillations" (CPO) was replaced by "population coherent oscillations" (PCO), "bleaching" - by "clearing", and "bleachable absorber " - by "clearable absorber". Here we present original version of the pape